Micro-electromechanical fluid ejection mechanism having a shape memory alloy actuator

ABSTRACT

Provided is a micro-electromechanical fluid ejection mechanism. The mechanism includes a substrate defining an ink passage in fluid communication with a tapered ink chamber having an ink ejection port, as well as a shape memory alloy (SMA) actuator arranged within the chamber. The actuator is configured to straighten when heated and to return to a bent state upon subsequent cooling to facilitate ejection of ink via the ejection port.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a Continuation of U.S. application Ser. No.11/525,857 filed on Sep. 25, 2006, which is a Continuation of U.S.application Ser. No. 11/064,011 filed on Feb. 24, 2005, now issued U.S.Pat. No. 7,178,903 which is a Continuation of U.S. application Ser. No.10/893,380 filed on Jul. 19, 2004, now issued U.S. Pat. No. 6,938,992,which is a Continuation of U.S. application Ser. No. 10/307,348 filed onDec. 2, 2002, now issued as U.S. Pat. No. 6,764,166, which is aContinuation of U.S. application Ser. No. 09/113,122 filed on Jul. 10,1998, now issued U.S. Pat. No. 6,557,977, the entire contents of whichare herein incorporated by reference.

The following Australian provisional patent applications are herebyincorporated by reference. For the purposes of location andidentification, US patents/patent applications identified by their USpatent/patent application serial numbers (USSN) are listed alongside theAustralian applications from which the US patents/patent applicationsclaim the right of priority.

US PATENT/PATENT CROSS-REFERENCED APPLICATION AUSTRALIAN (Claiming Rightof Priority Provisional Patent from Australian Provisional ApplicationNo. Application) Docket No. PO7991 6,750,901 ART01US PO8505 6,476,863ART02US PO7988 6,788,336 ART03US PO9395 6,322,181 ART04US PO80176,597,817 ART06US PO8014 6,227,648 ART07US PO8025 6,727,948 ART08USPO8032 6,690,419 ART09US PO7999 6,727,951 ART10US PO8030 6,196,541ART13US PO7997 6,195,150 ART15US PO7979 6,362,868 ART16US PO79786,831,681 ART18US PO7982 6,431,669 ART19US PO7989 6,362,869 ART20USPO8019 6,472,052 ART21US PO7980 6,356,715 ART22US PO8018 6,894,694ART24US PO7938 6,636,216 ART25US PO8016 6,366,693 ART26US PO80246,329,990 ART27US PO7939 6,459,495 ART29US PO8501 6,137,500 ART30USPO8500 6,690,416 ART31US PO7987 7,050,143 ART32US PO8022 6,398,328ART33US PO8497 7,110,024 ART34US PO8020 6,431,704 ART38US PO85046,879,341 ART42US PO8000 6,415,054 ART43US PO7934 6,665,454 ART45USPO7990 6,542,645 ART46US PO8499 6,486,886 ART47US PO8502 6,381,361ART48US PO7981 6,317,192 ART50US PO7986 6,850,274 ART51US PO798309/113,054 ART52US PO8026 6,646,757 ART53US PO8028 6,624,848 ART56USPO9394 6,357,135 ART57US PO9397 6,271,931 ART59US PO9398 6,353,772ART60US PO9399 6,106,147 ART61US PO9400 6,665,008 ART62US PO94016,304,291 ART63US PO9403 6,305,770 ART65US PO9405 6,289,262 ART66USPP0959 6,315,200 ART68US PP1397 6,217,165 ART69US PP2370 6,786,420DOT01US PO8003 6,350,023 Fluid01US PO8005 6,318,849 Fluid02US PO80666,227,652 IJ01US PO8072 6,213,588 IJ02US PO8040 6,213,589 IJ03US PO80716,231,163 IJ04US PO8047 6,247,795 IJ05US PO8035 6,394,581 IJ06US PO80446,244,691 IJ07US PO8063 6,257,704 IJ08US PO8057 6,416,168 IJ09US PO80566,220,694 IJ10US PO8069 6,257,705 IJ11US PO8049 6,247,794 IJ12US PO80366,234,610 IJ13US PO8048 6,247,793 IJ14US PO8070 6,264,306 IJ15US PO80676,241,342 IJ16US PO8001 6,247,792 IJ17US PO8038 6,264,307 IJ18US PO80336,254,220 IJ19US PO8002 6,234,611 IJ20US PO8068 6,302,528 IJ21US PO80626,283,582 IJ22US PO8034 6,239,821 IJ23US PO8039 6,338,547 IJ24US PO80416,247,796 IJ25US PO8004 6,557,977 IJ26US PO8037 6,390,603 IJ27US PO80436,362,843 IJ28US PO8042 6,293,653 IJ29US PO8064 6,312,107 IJ30US PO93896,227,653 IJ31US PO9391 6,234,609 IJ32US PP0888 6,238,040 IJ33US PP08916,188,415 IJ34US PP0890 6,227,654 IJ35US PP0873 6,209,989 IJ36US PP09936,247,791 IJ37US PP0890 6,336,710 IJ38US PP1398 6,217,153 IJ39US PP25926,416,167 IJ40US PP2593 6,243,113 IJ41US PP3991 6,283,581 IJ42US PP39876,247,790 IJ43US PP3985 6,260,953 IJ44US PP3983 6,267,469 IJ45US PO79356,224,780 IJM01US PO7936 6,235,212 IJM02US PO7937 6,280,643 IJM03USPO8061 6,284,147 IJM04US PO8054 6,214,244 IJM05US PO8065 6,071,750IJM06US PO8055 6,267,905 IJM07US PO8053 6,251,298 IJM08US PO80786,258,285 IJM09US PO7933 6,225,138 IJM10US PO7950 6,241,904 IJM11USPO7949 6,299,786 IJM12US PO8060 6,866,789 IJM13US PO8059 6,231,773IJM14US PO8073 6,190,931 IJM15US PO8076 6,248,249 IJM16US PO80756,290,862 IJM17US PO8079 6,241,906 IJM18US PO8050 6,565,762 IJM19USPO8052 6,241,905 IJM20US PO7948 6,451,216 IJM21US PO7951 6,231,772IJM22US PO8074 6,274,056 IJM23US PO7941 6,290,861 IJM24US PO80776,248,248 IJM25US PO8058 6,306,671 IJM26US PO8051 6,331,258 IJM27USPO8045 6,110,754 IJM28US PO7952 6,294,101 IJM29US PO8046 6,416,679IJM30US PO9390 6,264,849 IJM31US PO9392 6,254,793 IJM32US PP08896,235,211 IJM35US PP0887 6,491,833 IJM36US PP0882 6,264,850 IJM37USPP0874 6,258,284 IJM38US PP1396 6,312,615 IJM39US PP3989 6,228,668IJM40US PP2591 6,180,427 IJM41US PP3990 6,171,875 IJM42US PP39866,267,904 IJM43US PP3984 6,245,247 IJM44US PP3982 6,315,914 IJM45USPP0895 6,231,148 IR01US PP0869 6,293,658 IR04US PP0887 6,614,560 IR05USPP0885 6,238,033 IR06US PP0884 6,312,070 IR10US PP0886 6,238,111 IR12USPP0877 6,378,970 IR16US PP0878 6,196,739 IR17US PP0883 6,270,182 IR19USPP0880 6,152,619 IR20US PO8006 6,087,638 MEMS02US PO8007 6,340,222MEMS03US PO8010 6,041,600 MEMS05US PO8011 6,299,300 MEMS06US PO79476,067,797 MEMS07US PO7944 6,286,935 MEMS09US PO7946 6,044,646 MEMS10USPP0894 6,382,769 MEMS13US

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to ink jet printing and in particulardiscloses a shape memory alloy ink jet printer.

The present invention further relates to the field of drop on demand inkjet printing.

BACKGROUND OF THE INVENTION

Many different types of printing have been invented, a large number ofwhich are presently in use. The known forms of print have a variety ofmethods for marking the print media with a relevant marking media.Commonly used forms of printing include offset printing, laser printingand copying devices, dot matrix type impact printers, thermal paperprinters, film recorders, thermal wax printers, dye sublimation printersand ink jet printers both of the drop on demand and continuous flowtype. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

In recent years, the field of ink jet printing, wherein each individualpixel of ink is derived from one or more ink nozzles has becomeincreasingly popular primarily due to its inexpensive and versatilenature.

Many different techniques on ink jet printing have been invented. For asurvey of the field, reference is made to an article by J Moore,“Non-Impact Printing: Introduction and Historical Perspective”, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

Ink Jet printers themselves come in many different types. Theutilization of a continuous stream ink in ink jet printing appears todate back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hanselldiscloses a simple form of continuous stream electro-static ink jetprinting.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of acontinuous ink jet printing including the step wherein the ink jetstream is modulated by a high frequency electro-static field so as tocause drop separation. This technique is still utilized by severalmanufacturers including Elmjet and Scitex (see also U.S. Pat. No.3,373,437 by Sweet et al)

Piezoelectric ink jet printers are also one form of commonly utilizedink jet printing device. Piezoelectric systems are disclosed by Kyseret. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragmmode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) whichdiscloses a squeeze mode of operation of a piezoelectric crystal, Stemmein U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectricoperation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectricpush mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No.4,584,590 which discloses a shear mode type of piezoelectric transducerelement.

Recently, thermal ink jet printing has become an extremely popular formof ink jet printing. The ink jet printing techniques include thosedisclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S.Pat. No. 4,490,728. Both the aforementioned references disclosed ink jetprinting techniques rely upon the activation of an electrothermalactuator which results in the creation of a bubble in a constrictedspace, such as a nozzle, which thereby causes the ejection of ink froman aperture connected to the confined space onto a relevant print media.Printing devices utilizing the electro-thermal actuator are manufacturedby manufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printingtechnologies are available. Ideally, a printing technology should have anumber of desirable attributes. These include inexpensive constructionand operation, high speed operation, safe and continuous long termoperation etc. Each technology may have its own advantages anddisadvantages in the areas of cost, speed, quality, reliability, powerusage, simplicity of construction operation, durability and consumables.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide for a new form ofink jet printing device that utilizes a shape memory alloy in itsactivation method.

According to a first aspect of the invention, there is provided amicro-electromechanical fluid ejection mechanism, the fluid ejectionmechanism comprising

a substrate that incorporates drive circuitry;

a nozzle chamber structure arranged on the substrate to define a nozzlechamber and a fluid ejection port in fluid communication with the nozzlechamber; and

an actuator that is fast at one end with the substrate and that extendsinto the nozzle chamber, the actuator comprising

-   -   an actuating member that is connected to the drive circuitry and        anchored at one end to the substrate, the actuating member being        displaceable between a quiescent position and an active position        to eject fluid from the ejection port, at least a portion of the        actuating member being of a shape memory alloy which is        configured so that, when the shape memory alloy makes a phase        transformation, the actuating member is displaced between the        quiescent and active positions, the actuating member being        connected to the drive circuitry so that the shape memory alloy        can be heated above its phase change temperature on receipt of        an electrical signal from the drive circuitry.

The actuating member may incorporate a heating circuit of the shapememory alloy, the heating circuit being connected to the drive circuitryof the substrate.

The actuating member may be a laminated structure, with the heatercircuit defining one layer of the actuating member.

The actuating member may include a pre-stressing layer positioned on,and mechanically fast with, the heating circuit. The shape memory alloymay have a generally planar form when in the austenitic phase and thepre-stressing layer may serve to curl the actuating member away from theejection port when the shape memory alloy is in the martensitic phasesuch that, when heated, the shape memory alloy drives the actuatingmember into a planar form, thereby ejecting a drop of ink from theejection port.

The shape memory alloy may be a nickel titanium alloy. The pre-stressinglayer may be high stress silicon nitride.

The heating circuit may be interposed between the pre-stressing layerand a stress reference layer for the pre-stressing layer.

The nozzle chamber structure may be defined by the substrate as a resultof an etching process carried out on the substrate, such that one of thelayers of the substrate defines the ejection port on one side of thesubstrate and the actuator is positioned on an opposite side of thesubstrate.

According to a second aspect of the present invention there is provideda method of ejecting ink from a chamber comprising the steps of: a)providing a cantilevered beam actuator incorporating a shape memoryalloy; and b) transforming said shape memory alloy from its martensiticphase to its austenitic phase or vice versa to cause the ink to ejectfrom said chamber. Further, the actuator comprises a conductive shapememory alloy panel in a quiescent state and which transfers to an inkejection state upon heating thereby causing said ink ejection from thechamber. Preferably, the heating occurs by means of passing a currentthrough the shape memory alloy. The chamber is formed from acrystallographic etch of a silicon wafer so as to have one surface ofthe chamber substantially formed by the actuator. Advantageously, theactuator is formed from a conductive shape memory alloy arranged in aserpentine form and is attached to one wall of the chamber opposite anozzle port from which ink is ejected. Further, the nozzle port isformed by the back etching of a silicon wafer to the epitaxial layer andetching a nozzle port hole in the epitaxial layer. The crystallographicetch includes providing side wall slots of non-etched layers of aprocessed silicon wafer so as to the extend the dimensions of thechamber as a result of the crystallographic etch process. Preferably,the shape memory alloy comprises nickel titanium alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings which:

FIG. 1 is an exploded perspective view of a single ink jet nozzle asconstructed in accordance with the preferred embodiment;

FIG. 2 is a top cross sectional view of a single ink jet nozzle in itsquiescent state taken along line A-A in FIG. 1;

FIG. 3 is a top cross sectional view of a single ink jet nozzle in itsactuated state taken along line A-A in FIG. 1;

FIG. 4 provides a legend of the materials indicated in FIG. 5 to 15; and

FIG. 5 to FIG. 15 illustrate sectional views of the manufacturing stepsin one form of construction of an ink jet printhead nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, shape memory materials are utilized toconstruct an actuator suitable for injecting ink from the nozzle of anink chamber.

Turning to FIG. 1, there is illustrated an exploded perspective view 10of a single ink jet nozzle as constructed in accordance with thepreferred embodiment. The ink jet nozzle 10 is constructed from asilicon wafer base utilizing back etching of the wafer to a boron dopedepitaxial layer. Hence, the ink jet nozzle 10 comprises a lower layer 11which is constructed from boron doped silicon. The boron doped siliconlayer is also utilized a crystallographic etch stop layer. The nextlayer comprises the silicon layer 12 that includes a crystallographicpit 13 having side walls etched at the usual angle of 54.74. The layer12 also includes the various required circuitry and transistors forexample, CMOS layer (not shown). After this, a 0.5 micron thick thermalsilicon oxide layer 15 is grown on top of the silicon wafer 12.

After this, comes various layers which can comprise a two level metalCMOS process layers which provide the metal interconnect for the CMOStransistors formed within the layer 12. The various metal pathways etc.are not shown in FIG. 1 but for two metal interconnects 18, 19 whichprovide interconnection between a shape memory alloy layer 20 and theCMOS metal layers 16. The shape memory metal layer is next and is shapedin the form of a serpentine coil to be heated by end interconnect/viaportions 21,23. A top nitride layer 22 is provided for overallpassivation and protection of lower layers in addition to providing ameans of inducing tensile stress to curl upwards the shape memory alloylayer 20 in its quiescent state.

The preferred embodiment relies upon the thermal transition of a shapememory alloy 20 (SMA) from its martensitic phase to its austeniticphase. The basis of a shape memory effect is a martensitictransformation which creates a polydemane phase upon cooling. Thispolydemane phase accommodates finite reversible mechanical deformationswithout significant changes in the mechanical self energy of the system.Hence, upon re-transformation to the austenitic state the system returnsto its former macroscopic state to displaying the well known mechanicalmemory. The thermal transition is achieved by passing an electricalcurrent through the SMA. The actuator layer 20 is suspended at theentrance to a nozzle chamber connected via leads 18, 19 to the lowerlayers.

In FIG. 2, there is shown a cross-section of a single nozzle 10 when inits quiescent state, the section basically being taken through the lineA-A of FIG. 1. The actuator 30 is bent away from the nozzle when in itsquiescent state. In FIG. 3, there is shown a corresponding cross-sectionfor a single nozzle 10 when in an actuated state. When energized, theactuator 30 straightens, with the corresponding result that the ink ispushed out of the nozzle. The process of energizing the actuator 30requires supplying enough energy to raise the SMA above its transitiontemperature, and to provide the latent heat of transformation to the SMA20.

Obviously, the SMA martensitic phase must be pre-stressed to achieve adifferent shape from the austenitic phase. For printheads with manythousands of nozzles, it is important to achieve this pre-stressing in abulk manner. This is achieved by depositing the layer of silicon nitride22 using Plasma Enhanced Chemical Vapour Deposition (PECVD) at around300° C. over the SMA layer. The deposition occurs while the SMA is inthe austenitic shape. After the printhead cools to room temperature thesubstrate under the SMA bend actuator is removed by chemical etching ofa sacrificial substance. The silicon nitride layer 22 is under tensilestress, and causes the actuator to curl upwards. The weak martensiticphase of the SMA provides little resistance to this curl. When the SMAis heated to its austenitic phase, it returns to the flat shape intowhich it was annealed during the nitride deposition. The transformationbeing rapid enough to result in the ejection of ink from the nozzlechamber.

There is one SMA bend actuator 30 for each nozzle. One end 31 of the SMAbend actuator is mechanically connected to the substrate. The other endis free to move under the stresses inherent in the layers.

Returning to FIG. 1 the actuator layer is therefore composed of threelayers:

1. An SiO₂ lower layer 15. This layer acts as a stress ‘reference’ forthe nitride tensile layer. It also protects the SMA from thecrystallographic silicon etch that forms the nozzle chamber. This layercan be formed as part of the standard CMOS process for the activeelectronics of the printhead.

2. A SMA heater layer 20. A SMA such as nickel titanium (NiTi) alloy isdeposited and etched into a serpentine form to increase the electricalresistance.

3. A silicon nitride top layer 22. This is a thin layer of highstiffness which is deposited using PECVD. The nitride stoichiometry isadjusted to achieve a layer with significant tensile stress at roomtemperature relative to the SiO₂ lower layer. Its purpose is to bend theactuator at the low temperature martensitic phase.

As noted previously the ink jet nozzle of FIG. 1 can be constructed byutilizing a silicon wafer having a buried boron epitaxial layer. The 0.5micron thick dioxide layer 15 is then formed having side slots 45 whichare utilized in a subsequent crystallographic etch. Next, the variousCMOS layers 16 are formed including drive and control circuitry (notshown). The SMA layer 20 is then created on top of layers 15/16 andbeing interconnected with the drive circuitry. Subsequently, a siliconnitride layer 22 is formed on top. Each of the layers 15, 16, 22 includethe various slots eg. 45 which are utilized in a subsequentcrystallographic etch. The silicon wafer is subsequently thinned bymeans of back etching with the etch stop being the boron layer 11.Subsequent boron etching forms the nozzle hole eg. 47 and rim 46 (FIG.3). Subsequently, the chamber proper is formed by means of acrystallographic etch with the slots 45 defining the extent of the etchwithin the silicon oxide layer 12.

A large array of nozzles can be formed on the same wafer which in turnis attached to an ink chamber for filling the nozzle chambers.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet printheads operating in accordance with theprinciples taught by the present embodiment can proceed utilizing thefollowing steps:

1. Using a double sided polished wafer deposit 3 microns of epitaxialsilicon heavily doped with boron.

2. Deposit 10 microns of epitaxial silicon, either p-type or n-type,depending upon the CMOS process used.

3. Complete drive transistors, data distribution, and timing circuitsusing a 0.5 micron, one poly, 2 metal CMOS process. This step is shownin FIG. 5. For clarity, these diagrams may not be to scale, and may notrepresent a cross section though any single plane of the nozzle. FIG. 4is a key to representations of various materials in these manufacturingdiagrams, and those of other cross referenced ink jet configurations.

4. Etch the CMOS oxide layers down to silicon or aluminum using Mask 1.This mask defines the nozzle chamber, and the edges of the printheadschips. This step is shown in FIG. 6.

5. Crystallographically etch the exposed silicon using, for example, KOHor EDP (ethylenediamine pyrocatechol). This etch stops on <111>crystallographic planes, and on the boron doped silicon buried layer.This step is shown in FIG. 7.

6. Deposit 12 microns of sacrificial material. Planarize down to oxideusing CMP. The sacrificial material temporarily fills the nozzle cavity.This step is shown in FIG. 8.

7. Deposit 0.1 microns of high stress silicon nitride (Si3N4).

8. Etch the nitride layer using Mask 2. This mask defines the contactvias from the shape memory heater to the second-level metal contacts.

9. Deposit a seed layer.

10. Spin on 2 microns of resist, expose with Mask 3, and develop. Thismask defines the shape memory wire embedded in the paddle. The resistacts as an electroplating mold. This step is shown in FIG. 9.

11. Electroplate 1 micron of Nitinol. Nitinol is a ‘shape memory’ alloyof nickel and titanium, developed at the Naval Ordnance Laboratory inthe US (hence Ni-Ti-NOL). A shape memory alloy can be thermally switchedbetween its weak martensitic state and its high stiffness austenicstate.

12. Strip the resist and etch the exposed seed layer. This step is shownin FIG. 10.

13. Wafer probe. All electrical connections are complete at this point,bond pads are accessible, and the chips are not yet separated.

14. Deposit 0.1 microns of high stress silicon nitride. High stressnitride is used so that once the sacrificial material is etched, and thepaddle is released, the stress in the nitride layer will bend therelatively weak martensitic phase of the shape memory alloy. As theshape memory alloy—in its austenic phase—is flat when it is annealed bythe relatively high temperature deposition of this silicon nitridelayer, it will return to this flat state when electrothermally heated.

15. Mount the wafer on a glass blank and back-etch the wafer using KOHwith no mask. This etch thins the wafer and stops at the buried borondoped silicon layer. This step is shown in FIG. 11.

16. Plasma back-etch the boron doped silicon layer to a depth of 1micron using Mask 4. This mask defines the nozzle rim. This step isshown in FIG. 12.

17. Plasma back-etch through the boron doped layer using Mask 5. Thismask defines the nozzle, and the edge of the chips. At this stage, thechips are still mounted on the glass blank. This step is shown in FIG.13.

18. Strip the adhesive layer to detach the chips from the glass blank.Etch the sacrificial layer. This process completely separates the chips.This step is shown in FIG. 14.

19. Mount the printheads in their packaging, which may be a moldedplastic former incorporating ink channels which supply different colorsof ink to the appropriate regions of the front surface of the wafer.

20. Connect the printheads to their interconnect systems.

21. Hydrophobize the front surface of the printheads.

22. Fill with ink and test the completed printheads. A filled nozzle isshown in FIG. 15.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiment without departing from the spirit orscope of the invention as broadly described. The present embodiment is,therefore, to be considered in all respects to be illustrative and notrestrictive.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing systems including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters, high speed pagewidth printers, notebook computers with inbuiltpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic‘minilabs’, video printers, PHOTO CD (PHOTO CD is a registered trademarkof the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per printhead, but is a majorimpediment to the fabrication of pagewidth printheads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table under the heading Cross References toRelated Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems.

For ease of manufacture using standard process equipment, the printheadis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the printhead is 100 mmlong, with a width which depends upon the ink jet type. The smallestprinthead designed is IJ38, which is 0.35 mm wide, giving a chip area of35 square mm. The printheads each contain 19,200 nozzles plus data andcontrol circuitry.

Ink is supplied to the back of the print head by injection moldedplastic ink channels. The molding requires 50 micron features, which canbe created using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprinthead is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-On-Demand Ink Jets

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. These are designated IJ01 toIJ45 which match the docket numbers in the table under the heading CrossReferenced to Related Application.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet printheads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The IJ01 to IJ45 series are also listed in the examples column. In somecases, a print technology may be listed more than once in a table, whereit shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

Description Advantages Disadvantages Examples ACTUATOR MECHANISM(APPLIED ONLY TO SELECTED INK DROPS) Thermal An electrothermal Largeforce High power Canon bubble heater heats the generated Ink carrierBubblejet 1979 ink to above Simple limited to water Endo et al GBboiling point, construction Low patent 2,007,162 transferring No movingefficiency Xerox heater- significant heat to parts High in-pit 1990 theaqueous ink. A Fast operation temperatures Hawkins et al bubblenucleates Small chip required U.S. Pat. No. 4,899,181 and quickly forms,area required for High Hewlett- expelling the ink. actuator mechanicalPackard TIJ The efficiency of stress 1982 Vaught et the process is low,Unusual al U.S. Pat. No. with typically less materials 4,490,728 than0.05% of the required electrical energy Large drive being transformedtransistors into kinetic energy Cavitation of the drop. causes actuatorfailure Kogation reduces bubble formation Large print heads aredifficult to fabricate Piezo- A piezoelectric Low power Very large Kyseret al electric crystal such as consumption area required for U.S. Pat.No. 3,946,398 lead lanthanum Many ink actuator Zoltan U.S. Pat. No.zirconate (PZT) is types can be Difficult to 3,683,212 electrically usedintegrate with 1973 Stemme activated, and Fast operation electronicsU.S. Pat. No. 3,747,120 either expands, High High voltage Epson Stylusshears, or bends to efficiency drive transistors Tektronix applypressure to required IJ04 the ink, ejecting Full drops. pagewidth printheads impractical due to actuator size Requires electrical poling inhigh field strengths during manufacture Electro- An electric field isLow power Low Seiko Epson, strictive used to activate consumptionmaximum strain Usui et all JP electrostriction in Many ink (approx.0.01%) 253401/96 relaxor materials types can be Large area IJ04 such aslead used required for lanthanum Low thermal actuator due to zirconatetitanate expansion low strain (PLZT) or lead Electric field Responsemagnesium strength required speed is niobate (PMN). (approx. 3.5 V/μm)marginal (~10 μs) can be High voltage generated drive transistorswithout required difficulty Full Does not pagewidth print requireelectrical heads poling impractical due to actuator size Ferro- Anelectric field is Low power Difficult to IJ04 electric used to induce aconsumption integrate with phase transition Many ink electronics betweenthe types can be Unusual antiferroelectric used materials such as (AFE)and Fast operation PLZSnT are ferroelectric (FE) (<1 μs) required phase.Perovskite Relatively Actuators materials such as high longitudinalrequire a large tin modified lead strain area lanthanum High zirconatetitanate efficiency (PLZSnT) exhibit Electric field large strains of upstrength of to 1% associated around 3 V/μm with the AFE to can bereadily FE phase provided transition. Electro- Conductive plates Lowpower Difficult to IJ02, IJ04 static are separated by a consumptionoperate plates compressible or Many ink electrostatic fluid dielectrictypes can be devices in an (usually air). Upon used aqueous applicationof a Fast operation environment voltage, the plates The attract eachother electrostatic and displace ink, actuator will causing dropnormally need to ejection. The be separated conductive plates from theink may be in a comb Very large or honeycomb area required to structure,or achieve high stacked to increase forces the surface area High voltageand therefore the drive transistors force. may be required Fullpagewidth print heads are not competitive due to actuator size Electro-A strong electric Low current High voltage 1989 Saito et static pullfield is applied to consumption required al, U.S. Pat. No. on ink theink, whereupon Low May be 4,799,068 electrostatic temperature damaged by1989 Miura et attraction sparks due to air al, U.S. Pat. No. acceleratesthe ink breakdown 4,810,954 towards the print Required field Tone-jetmedium. strength increases as the drop size decreases High voltage drivetransistors required Electrostatic field attracts dust Permanent Anelectromagnet Low power Complex IJ07, IJ10 magnet directly attracts aconsumption fabrication electro- permanent magnet, Many ink Permanentmagnetic displacing ink and types can be magnetic causing drop usedmaterial such as ejection. Rare Fast operation Neodymium Iron earthmagnets with High Boron (NdFeB) a field strength efficiency required.around 1 Tesla can Easy High local be used. Examples extension fromcurrents required are: Samarium single nozzles to Copper Cobalt (SaCo)and pagewidth print metalization magnetic materials heads should be usedin the neodymium for long iron boron family electromigration (NdFeB,lifetime and low NdDyFeBNb, resistivity NdDyFeB, etc) Pigmented inks areusually infeasible Operating temperature limited to the Curietemperature (around 540 K) Soft A solenoid Low power Complex IJ01, IJ05,magnetic induced a consumption fabrication IJ08, IJ10, IJ12, coremagnetic field in a Many ink Materials not IJ14, IJ15, IJ17 electro-soft magnetic core types can be usually present magnetic or yokefabricated used in a CMOS fab from a ferrous Fast operation such asNiFe, material such as High CoNiFe, or CoFe electroplated ironefficiency are required alloys such as Easy High local CoNiFe [1], CoFe,extension from currents required or NiFe alloys. single nozzles toCopper Typically, the soft pagewidth print metalization magneticmaterial heads should be used is in two parts, for long which areelectromigration normally held lifetime and low apart by a spring.resistivity When the solenoid Electroplating is actuated, the two isrequired parts attract, High displacing the ink. saturation flux densityis required (2.0-2.1 T is achievable with CoNiFe [1]) Lorenz The Lorenzforce Low power Force acts as a IJ06, IJ11, force acting on a currentconsumption twisting motion IJ13, IJ16 carrying wire in a Many inkTypically, magnetic field is types can be only a quarter of utilized.used the solenoid This allows the Fast operation length providesmagnetic field to High force in a useful be supplied efficiencydirection externally to the Easy High local print head, for extensionfrom currents required example with rare single nozzles to Copper earthpermanent pagewidth print metalization magnets. heads should be usedOnly the current for long carrying wire need electromigration befabricated on lifetime and low the print-head, resistivity simplifyingPigmented materials inks are usually requirements. infeasible Magneto-The actuator uses Many ink Force acts as a Fischenbeck, striction thegiant types can be twisting motion U.S. Pat. No. 4,032,929magnetostrictive used Unusual IJ25 effect of materials Fast operationmaterials such as such as Terfenol-D Easy Terfenol-D are (an alloy ofextension from required terbium, single nozzles to High local dysprosiumand pagewidth print currents required iron developed at heads Copper theNaval High force is metalization Ordnance available should be usedLaboratory, hence for long Ter-Fe-NOL). For electromigration bestefficiency, the lifetime and low actuator should be resistivitypre-stressed to Pre-stressing approx. 8 MPa. may be required Surface Inkunder positive Low power Requires Silverbrook, tension pressure is heldin consumption supplementary EP 0771 658 A2 reduction a nozzle bysurface Simple force to effect and related tension. The constructiondrop separation patent surface tension of No unusual Requiresapplications the ink is reduced materials special ink below the bubblerequired in surfactants threshold, causing fabrication Speed may be theink to egress High limited by from the nozzle. efficiency surfactantEasy properties extension from single nozzles to pagewidth print headsViscosity The ink viscosity Simple Requires Silverbrook, reduction islocally reduced construction supplementary EP 0771 658 A2 to selectwhich No unusual force to effect and related drops are to be materialsdrop separation patent ejected. A required in Requires applicationsviscosity reduction fabrication special ink can be achieved Easyviscosity electrothermally extension from properties with most inks, butsingle nozzles to High speed is special inks can be pagewidth printdifficult to engineered for a heads achieve 100:1 viscosity Requiresreduction. oscillating ink pressure A high temperature difference(typically 80 degrees) is required Acoustic An acoustic wave Can operateComplex 1993 is generated and without a nozzle drive circuitryHadimioglu et focussed upon the plate Complex al, EUP 550,192 dropejection fabrication 1993 Elrod et region. Low al, EUP 572,220efficiency Poor control of drop position Poor control of drop volumeThermo- An actuator which Low power Efficient IJ03, IJ09, elastic reliesupon consumption aqueous IJ17, IJ18, IJ19, bend differential Many inkoperation IJ20, IJ21, IJ22, actuator thermal expansion types can berequires a IJ23, IJ24, IJ27, upon Joule heating used thermal insulatorIJ28, IJ29, IJ30, is used. Simple planar on the hot side IJ31, IJ32,IJ33, fabrication Corrosion IJ34, IJ35, IJ36, Small chip prevention canIJ37, IJ38, IJ39, area required for be difficult IJ40, IJ41 eachactuator Pigmented Fast operation inks may be High infeasible, asefficiency pigment particles CMOS may jam the compatible bend actuatorvoltages and currents Standard MEMS processes can be used Easy extensionfrom single nozzles to pagewidth print heads High CTE A material with aHigh force Requires IJ09, IJ17, thermo- very high can be generatedspecial material IJ18, IJ20, IJ21, elastic coefficient of Three (e.g.PTFE) IJ22, IJ23, IJ24, actuator thermal expansion methods of Requires aIJ27, IJ28, IJ29, (CTE) such as PTFE deposition PTFE deposition IJ30,IJ31, IJ42, polytetrafluoroethylene are under process, which is IJ43,IJ44 (PTFE) is development: not yet standard used. As high CTE chemicalvapor in ULSI fabs materials are deposition PTFE usually non- (CVD),spin deposition conductive, a coating, and cannot be heater fabricatedevaporation followed with from a conductive PTFE is a high temperaturematerial is candidate for (above 350° C.) incorporated. A 50 μm lowdielectric processing long PTFE constant Pigmented bend actuator withinsulation in inks may be polysilicon heater ULSI infeasible, as and 15mW power Very low pigment particles input can provide power may jam the180 μN force and consumption bend actuator 10 μm deflection. Many inkActuator motions types can be include: used Bend Simple planar Pushfabrication Buckle Small chip Rotate area required for each actuatorFast operation High efficiency CMOS compatible voltages and currentsEasy extension from single nozzles to pagewidth print heads Conductive Apolymer with a High force Requires IJ24 polymer high coefficient of canbe generated special materials thermo- thermal expansion Very lowdevelopment elastic (such as PTFE) is power (High CTE actuator dopedwith consumption conductive conducting Many ink polymer) substances totypes can be Requires a increase its used PTFE deposition conductivityto Simple planar process, which is about 3 orders of fabrication not yetstandard magnitude below Small chip in ULSI fabs that of copper. Thearea required for PTFE conducting each actuator deposition polymerexpands Fast operation cannot be when resistively High followed withheated. efficiency high temperature Examples of CMOS (above 350° C.)conducting compatible processing dopants include: voltages andEvaporation Carbon nanotubes currents and CVD Metal fibers Easydeposition Conductive extension from techniques polymers such as singlenozzles to cannot be used doped pagewidth print Pigmented polythiopheneheads inks may be Carbon granules infeasible, as pigment particles mayjam the bend actuator Shape A shape memory High force is Fatigue limitsIJ26 memory alloy such as TiNi available maximum alloy (also known as(stresses of number of cycles Nitinol - Nickel hundreds of Low strainTitanium alloy MPa) (1%) is required developed at the Large strain is toextend fatigue Naval Ordnance available (more resistance Laboratory) isthan 3%) Cycle rate thermally switched High limited by heat between itsweak corrosion removal martensitic state resistance Requires and itshigh Simple unusual stiffness austenic construction materials (TiNi)state. The shape of Easy The latent the actuator in its extension fromheat of martensitic state is single nozzles to transformation deformedrelative pagewidth print must be to the austenic heads provided shape.The shape Low voltage High current change causes operation operationejection of a drop. Requires pre- stressing to distort the martensiticstate Linear Linear magnetic Linear Requires IJ12 Magnetic actuatorsinclude Magnetic unusual Actuator the Linear actuators can besemiconductor Induction Actuator constructed with materials such as(LIA), Linear high thrust, long soft magnetic Permanent Magnet travel,and high alloys (e.g. Synchronous efficiency using CoNiFe) Actuatorplanar Some varieties (LPMSA), Linear semiconductor also requireReluctance fabrication permanent Synchronous techniques magneticActuator (LRSA), Long actuator materials such as Linear Switched travelis Neodymium iron Reluctance available boron (NdFeB) Actuator (LSRA),Medium force Requires and the Linear is available complex multi- StepperActuator Low voltage phase drive (LSA). operation circuitry High currentoperation BASIC OPERATION MODE Actuator This is the Simple Drop Thermalink directly simplest mode of operation repetition rate is jet pushesoperation: the No external usually limited Piezoelectric ink actuatordirectly fields required to around 10 kHz. ink jet supplies sufficientSatellite drops However, IJ01, IJ02, kinetic energy to can be avoided ifthis is not IJ03, IJ04, IJ05, expel the drop. drop velocity isfundamental to IJ06, IJ07, IJ09, The drop must less than 4 m/s themethod, but IJ11, IJ12, IJ14, have a sufficient Can be is related to theIJ16, IJ20, IJ22, velocity to efficient, refill method IJ23, IJ24, IJ25,overcome the depending upon normally used IJ26, IJ27, IJ28, surfacetension. the actuator used All of the drop IJ29, IJ30, IJ31, kineticenergy IJ32, IJ33, IJ34, must be IJ35, IJ36, IJ37, provided by the IJ38,IJ39, IJ40, actuator IJ41, IJ42, IJ43, Satellite drops IJ44 usually formif drop velocity is greater than 4.5 m/s Proximity The drops to be Verysimple Requires close Silverbrook, printed are print head proximity EP0771 658 A2 selected by some fabrication can between the and relatedmanner (e.g. be used print head and patent thermally induced The dropthe print media applications surface tension selection means or transferroller reduction of does not need to May require pressurized ink).provide the two print heads Selected drops are energy required printingalternate separated from the to separate the rows of the ink in thenozzle drop from the image by contact with the nozzle Monolithic printmedium or a color print heads transfer roller. are difficult Electro-The drops to be Very simple Requires very Silverbrook, static pullprinted are print head high electrostatic EP 0771 658 A2 on ink selectedby some fabrication can field and related manner (e.g. be usedElectrostatic patent thermally induced The drop field for smallapplications surface tension selection means nozzle sizes is Tone-Jetreduction of does not need to above air pressurized ink). provide thebreakdown Selected drops are energy required Electrostatic separatedfrom the to separate the field may attract ink in the nozzle drop fromthe dust by a strong electric nozzle field. Magnetic The drops to beVery simple Requires Silverbrook, pull on printed are print headmagnetic ink EP 0771 658 A2 ink selected by some fabrication can Inkcolors and related manner (e.g. be used other than black patentthermally induced The drop are difficult applications surface tensionselection means Requires very reduction of does not need to highmagnetic pressurized ink). provide the fields Selected drops are energyrequired separated from the to separate the ink in the nozzle drop fromthe by a strong nozzle magnetic field acting on the magnetic ink.Shutter The actuator High speed Moving parts IJ13, IJ17, moves a shutterto (>50 kHz) are required IJ21 block ink flow to operation can beRequires ink the nozzle. The ink achieved due to pressure pressure ispulsed reduced refill modulator at a multiple of the time Friction anddrop ejection Drop timing wear must be frequency. can be very consideredaccurate Stiction is The actuator possible energy can be very lowShuttered The actuator Actuators with Moving parts IJ08, IJ15, grillmoves a shutter to small travel can are required IJ18, IJ19 block inkflow be used Requires ink through a grill to Actuators with pressure thenozzle. The small force can modulator shutter movement be used Frictionand need only be equal High speed wear must be to the width of the (>50kHz) considered grill holes. operation can be Stiction is achievedpossible Pulsed A pulsed magnetic Extremely low Requires an IJ10magnetic field attracts an energy operation external pulsed pull on ‘inkpusher’ at the is possible magnetic field ink drop ejection No heatRequires pusher frequency. An dissipation special materials actuatorcontrols a problems for both the catch, which actuator and the preventsthe ink ink pusher pusher from Complex moving when a construction dropis not to be ejected. AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) NoneThe actuator Simplicity of Drop ejection Most ink jets, directly firesthe construction energy must be including ink drop, and there Simplicityof supplied by piezoelectric and is no external field operationindividual nozzle thermal bubble. or other Small physical actuator IJ01,IJ02, mechanism size IJ03, IJ04, IJ05, required. IJ07, IJ09, IJ11, IJ12,IJ14, IJ20, IJ22, IJ23, IJ24, IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31,IJ32, IJ33, IJ34, IJ35, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43,IJ44 Oscillating The ink pressure Oscillating ink Requires Silverbrook,ink oscillates, pressure can external ink EP 0771 658 A2 pressureproviding much of provide a refill pressure and related (including thedrop ejection pulse, allowing oscillator patent acoustic energy. Thehigher operating Ink pressure applications stimulation) actuator selectsspeed phase and IJ08, IJ13, which drops are to The actuators amplitudemust IJ15, IJ17, IJ18, be fired by may operate be carefully IJ19, IJ21selectively with much lower controlled blocking or energy Acousticenabling nozzles. Acoustic reflections in the The ink pressure lensescan be ink chamber oscillation may be used to focus the must be achievedby sound on the designed for vibrating the print nozzles head, orpreferably by an actuator in the ink supply. Media The print head is Lowpower Precision Silverbrook, proximity placed in close High accuracyassembly EP 0771 658 A2 proximity to the Simple print required andrelated print medium. head Paper fibers patent Selected dropsconstruction may cause applications protrude from the problems printhead further Cannot print than unselected on rough drops, and contactsubstrates the print medium. The drop soaks into the medium fast enoughto cause drop separation. Transfer Drops are printed High accuracy BulkySilverbrook, roller to a transfer roller Wide range of Expensive EP 0771658 A2 instead of straight print substrates Complex and related to theprint can be used construction patent medium. A Ink can be applicationstransfer roller can dried on the Tektronix hot also be used for transferroller melt proximity drop piezoelectric ink separation. jet Any of theIJ series Electro- An electric field is Low power Field strengthSilverbrook, static used to accelerate Simple print required for EP 0771658 A2 selected drops head separation of and related towards the printconstruction small drops is patent medium. near or above airapplications breakdown Tone-Jet Direct A magnetic field is Low powerRequires Silverbrook, magnetic used to accelerate Simple print magneticink EP 0771 658 A2 field selected drops of head Requires and relatedmagnetic ink construction strong magnetic patent towards the print fieldapplications medium. Cross The print head is Does not Requires IJ06,IJ16 magnetic placed in a require magnetic external magnet fieldconstant magnetic materials to be Current field. The Lorenz integratedin the densities may be force in a current print head high, resulting incarrying wire is manufacturing electromigration used to move the processproblems actuator. Pulsed A pulsed magnetic Very low Complex print IJ10magnetic field is used to power operation head field cyclically attracta is possible construction paddle, which Small print Magnetic pushes onthe ink. head size materials A small actuator required in print moves acatch, head which selectively prevents the paddle from moving. ACTUATORAMPLIFICATION OR MODIFICATION METHOD None No actuator Operational Manyactuator Thermal mechanical simplicity mechanisms Bubble Ink jetamplification is have insufficient IJ01, IJ02, used. The actuatortravel, or IJ06, IJ07, IJ16, directly drives the insufficient IJ25, IJ26drop ejection force, to process. efficiently drive the drop ejectionprocess Differential An actuator Provides High stresses Piezoelectricexpansion material expands greater travel in are involved IJ03, IJ09,bend more on one side a reduced print Care must be IJ17, IJ18, IJ19,actuator than on the other. head area taken that the IJ20, IJ21, IJ22,The expansion materials do not IJ23, IJ24, IJ27, may be thermal,delaminate IJ29, IJ30, IJ31, piezoelectric, Residual bend IJ32, IJ33,IJ34, magnetostrictive, resulting from IJ35, IJ36, IJ37, or other hightemperature IJ38, IJ39, IJ42, mechanism. The or high stress IJ43, IJ44bend actuator during formation converts a high force low travel actuatormechanism to high travel, lower force mechanism. Transient A trilayerbend Very good High stresses IJ40, IJ41 bend actuator where thetemperature are involved actuator two outside layers stability Care mustbe are identical. This High speed, as taken that the cancels bend due anew drop can materials do not to ambient be fired before delaminatetemperature and heat dissipates residual stress. The Cancels actuatoronly residual stress of responds to formation transient heating of oneside or the other. Reverse The actuator loads Better Fabrication IJ05,IJ11 spring a spring. When the coupling to the complexity actuator isturned ink High stress in off, the spring the spring releases. This canreverse the force/distance curve of the actuator to make it compatiblewith the force/time requirements of the drop ejection. Actuator A seriesof thin Increased Increased Some stack actuators are travel fabricationpiezoelectric ink stacked. This can Reduced drive complexity jets beappropriate voltage Increased IJ04 where actuators possibility ofrequire high short circuits due electric field to pinholes strength,such as electrostatic and piezoelectric actuators. Multiple Multiplesmaller Increases the Actuator IJ12, IJ13, actuators actuators are usedforce available forces may not IJ18, IJ20, IJ22, simultaneously to froman actuator add linearly, IJ28, IJ42, IJ43 move the ink. Each Multiplereducing actuator need actuators can be efficiency provide only apositioned to portion of the control ink flow force required. accuratelyLinear A linear spring is Matches low Requires print IJ15 Spring used totransform a travel actuator head area for the motion with small withhigher spring travel and high travel force into a longer requirementstravel, lower force Non-contact motion. method of motion transformationCoiled A bend actuator is Increases Generally IJ17, IJ21, actuatorcoiled to provide travel restricted to IJ34, IJ35 greater travel in aReduces chip planar reduced chip area. area implementations Planar dueto extreme implementations fabrication are relatively difficulty in easyto fabricate. other orientations. Flexure A bend actuator Simple meansCare must be IJ10, IJ19, bend has a small region of increasing taken notto IJ33 actuator near the fixture travel of a bend exceed the point,which flexes actuator elastic limit in much more readily the flexurearea than the remainder Stress of the actuator. distribution is Theactuator very uneven flexing is Difficult to effectively accuratelymodel converted from an with finite even coiling to an element analysisangular bend, resulting in greater travel of the actuator tip. Catch Theactuator Very low Complex IJ10 controls a small actuator energyconstruction catch. The catch Very small Requires either enables oractuator size external force disables movement Unsuitable for of an inkpusher pigmented inks that is controlled in a bulk manner. Gears Gearscan be used Low force, Moving parts IJ13 to increase travel low travelare required at the expense of actuators can be Several duration.Circular used actuator cycles gears, rack and Can be are requiredpinion, ratchets, fabricated using More complex and other gearingstandard surface drive electronics methods can be MEMS Complex used.processes construction Friction, friction, and wear are possible BuckleA buckle plate can Very fast Must stay S. Hirata et al, plate be used tochange movement within elastic “An Ink-jet a slow actuator achievablelimits of the Head Using into a fast motion. materials for Diaphragm Itcan also convert long device life Microactuator”, a high force, low Highstresses Proc. IEEE travel actuator into involved MEMS, February a hightravel, Generally 1996, pp 418-423. medium force high power IJ18, IJ27motion. requirement Tapered A tapered Linearizes the Complex IJ14magnetic magnetic pole can magnetic construction pole increase travel atforce/distance the expense of curve force. Lever A lever and Matches lowHigh stress IJ32, IJ36, fulcrum is used to travel actuator around theIJ37 transform a motion with higher fulcrum with small travel travel andhigh force into requirements a motion with Fulcrum area longer traveland has no linear lower force. The movement, and lever can also can beused for a reverse the fluid seal direction of travel. Rotary Theactuator is High Complex IJ28 impeller connected to a mechanicalconstruction rotary impeller. A advantage Unsuitable for small angularThe ratio of pigmented inks deflection of the force to travel ofactuator results in the actuator can a rotation of the be matched toimpeller vanes, the nozzle which push the ink requirements by againststationary varying the vanes and out of number of the nozzle. impellervanes Acoustic A refractive or No moving Large area 1993 lensdiffractive (e.g. parts required Hadimioglu et zone plate) Only relevantal, EUP 550,192 acoustic lens is for acoustic ink 1993 Elrod et used toconcentrate jets al, EUP 572,220 sound waves. Sharp A sharp point isSimple Difficult to Tone-jet conductive used to concentrate constructionfabricate using point an electrostatic standard VLSI field. processesfor a surface ejecting ink-jet Only relevant for electrostatic ink jetsACTUATOR MOTION Volume The volume of the Simple High energy is Hewlett-expansion actuator changes, construction in typically Packard Thermalpushing the ink in the case of required to Ink jet all directions.thermal ink jet achieve volume Canon expansion. This Bubblejet leads tothermal stress, cavitation, and kogation in thermal ink jetimplementations Linear, The actuator Efficient High IJ01, IJ02, normalto moves in a coupling to ink fabrication IJ04, IJ07, IJ11, chipdirection normal to drops ejected complexity may IJ14 surface the printhead normal to the be required to surface. The surface achieve nozzle istypically perpendicular in the line of motion movement. Parallel to Theactuator Suitable for Fabrication IJ12, IJ13, chip moves parallel toplanar complexity IJ15, IJ33,, IJ34, surface the print head fabricationFriction IJ35, IJ36 surface. Drop Stiction ejection may still be normalto the surface. Membrane An actuator with a The effective Fabrication1982 Howkins push high force but area of the complexity U.S. Pat. No.4,459,601 small area is used actuator Actuator size to push a stiffbecomes the Difficulty of membrane that is membrane area integration ina in contact with the VLSI process ink. Rotary The actuator Rotarylevers Device IJ05, IJ08, causes the rotation may be used to complexityIJ13, IJ28 of some element, increase travel May have such a grill orSmall chip friction at a pivot impeller area point requirements Bend Theactuator bends A very small Requires the 1970 Kyser et when energized.change in actuator to be al U.S. Pat. No. This may be due to dimensionscan made from at 3,946,398 differential be converted to a least twodistinct 1973 Stemme thermal expansion, large motion. layers, or to haveU.S. Pat. No. 3,747,120 piezoelectric a thermal IJ03, IJ09, expansion,difference across IJ10, IJ19, IJ23, magnetostriction, the actuator IJ24,IJ25, IJ29, or other form of IJ30, IJ31, IJ33, relative IJ34, IJ35dimensional change. Swivel The actuator Allows Inefficient IJ06 swivelsaround a operation where coupling to the central pivot. This the netlinear ink motion motion is suitable force on the where there are paddleis zero opposite forces Small chip applied to opposite area sides of thepaddle, requirements e.g. Lorenz force. Straighten The actuator is Canbe used Requires IJ26, IJ32 normally bent, and with shape carefulbalance straightens when memory alloys of stresses to energized. wherethe ensure that the austenic phase is quiescent bend is planar accurateDouble The actuator bends One actuator Difficult to IJ36, IJ37, bend inone direction can be used to make the drops IJ38 when one element powertwo ejected by both is energized, and nozzles. bend directions bends theother Reduced chip identical. way when another size. A small element isNot sensitive efficiency loss energized. to ambient compared totemperature equivalent single bend actuators. Shear Energizing the Canincrease Not readily 1985 Fishbeck actuator causes a the effectiveapplicable to U.S. Pat. No. 4,584,590 shear motion in the travel ofother actuator actuator material. piezoelectric mechanisms actuatorsRadial The actuator Relatively High force 1970 Zoltan constrictionsqueezes an ink easy to fabricate required U.S. Pat. No. 3,683,212reservoir, forcing single nozzles Inefficient ink from a from glassDifficult to constricted nozzle. tubing as integrate with macroscopicVLSI processes structures Coil/ A coiled actuator Easy to Difficult toIJ17, IJ21, uncoil uncoils or coils fabricate as a fabricate for IJ34,IJ35 more tightly. The planar VLSI non-planar motion of the free processdevices end of the actuator Small area Poor out-of- ejects the ink.required, plane stiffness therefore low cost Bow The actuator bows Canincrease Maximum IJ16, IJ18, (or buckles) in the the speed of travel isIJ27 middle when travel constrained energized. Mechanically High forcerigid required Push-Pull Two actuators The structure Not readily IJ18control a shutter. is pinned at both suitable for ink One actuator pullsends, so has a jets which the shutter, and the high out-of- directlypush the other pushes it. plane rigidity ink Curl A set of actuatorsGood fluid Design IJ20, IJ42 inwards curl inwards to flow to thecomplexity reduce the volume region behind of ink that they the actuatorenclose. increases efficiency Curl A set of actuators RelativelyRelatively IJ43 outwards curl outwards, simple large chip areapressurizing ink in construction a chamber surrounding the actuators,and expelling ink from a nozzle in the chamber. Iris Multiple vanes HighHigh IJ22 enclose a volume efficiency fabrication of ink. These Smallchip complexity simultaneously area Not suitable rotate, reducing forpigmented the volume inks between the vanes. Acoustic The actuator Theactuator Large area 1993 vibration vibrates at a high can be requiredfor Hadimioglu et frequency. physically efficient al, EUP 550,192distant from the operation at 1993 Elrod et ink useful al, EUP 572,220frequencies Acoustic coupling and crosstalk Complex drive circuitry Poorcontrol of drop volume and position None In various ink jet No movingVarious other Silverbrook, designs the parts tradeoffs are EP 0771 658A2 actuator does not required to and related move. eliminate patentmoving parts applications Tone-jet NOZZLE REFILL METHOD Surface This isthe normal Fabrication Low speed Thermal ink tension way that ink jetssimplicity Surface jet are refilled. After Operational tension forcePiezoelectric the actuator is simplicity relatively small ink jetenergized, it compared to IJ01-IJ07, typically returns actuator forceIJ10-IJ14, IJ16, rapidly to its Long refill IJ20, IJ22-IJ45 normalposition. time usually This rapid return dominates the sucks in airtotal repetition through the nozzle rate opening. The ink surfacetension at the nozzle then exerts a small force restoring the meniscusto a minimum area. This force refills the nozzle. Shuttered Ink to thenozzle High speed Requires IJ08, IJ13, oscillating chamber is Lowactuator common ink IJ15, IJ17, IJ18, ink provided at a energy, as thepressure IJ19, IJ21 pressure pressure that actuator need oscillatoroscillates at twice only open or May not be the drop ejection close theshutter, suitable for frequency. When a instead of pigmented inks dropis to be ejecting the ink ejected, the shutter drop is opened for 3 halfcycles: drop ejection, actuator return, and refill. The shutter is thenclosed to prevent the nozzle chamber emptying during the next negativepressure cycle. Refill After the main High speed, as Requires two IJ09actuator actuator has the nozzle is independent ejected a drop aactively refilled actuators per second (refill) nozzle actuator isenergized. The refill actuator pushes ink into the nozzle chamber. Therefill actuator returns slowly, to prevent its return from emptying thechamber again. Positive The ink is held a High refill Surface spillSilverbrook, ink slight positive rate, therefore a must be EP 0771 658A2 pressure pressure. After the high drop prevented and related ink dropis ejected, repetition rate is Highly patent the nozzle possiblehydrophobic applications chamber fills print head Alternative quickly assurface surfaces are for:, IJ01-IJ07, tension and ink requiredIJ10-IJ14, IJ16, pressure both IJ20, IJ22-IJ45 operate to refill thenozzle. METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Long inlet The inkinlet Design Restricts refill Thermal ink channel channel to thesimplicity rate jet nozzle chamber is Operational May result inPiezoelectric made long and simplicity a relatively large ink jetrelatively narrow, Reduces chip area IJ42, IJ43 relying on viscouscrosstalk Only partially drag to reduce effective inlet back-flow.Positive The ink is under a Drop selection Requires a Silverbrook, inkpositive pressure, and separation method (such as EP 0771 658 A2pressure so that in the forces can be a nozzle rim or and relatedquiescent state reduced effective patent some of the ink Fast refilltime hydrophobizing, applications drop already or both) to Possibleprotrudes from the prevent flooding operation of the nozzle. of theejection following: IJ01-IJ07, This reduces the surface of theIJ09-IJ12, pressure in the print head. IJ14, IJ16, IJ20, nozzle chamberIJ22,, IJ23-IJ34, which is required IJ36-IJ41, IJ44 to eject a certainvolume of ink. The reduction in chamber pressure results in a reductionin ink pushed out through the inlet. Baffle One or more The refill rateDesign HP Thermal baffles are placed is not as complexity Ink Jet in theinlet ink restricted as the May increase Tektronix flow. When the longinlet fabrication piezoelectric ink actuator is method. complexity (e.g.jet energized, the Reduces Tektronix hot rapid ink crosstalk meltmovement creates Piezoelectric eddies which print heads). restrict theflow through the inlet. The slower refill process is unrestricted, anddoes not result in eddies. Flexible In this method Significantly Notapplicable Canon flap recently disclosed reduces back- to most ink jetrestricts by Canon, the flow for edge- configurations inlet expandingactuator shooter thermal Increased (bubble) pushes on ink jet devicesfabrication a flexible flap that complexity restricts the inlet.Inelastic deformation of polymer flap results in creep over extended useInlet filter A filter is located Additional Restricts refill IJ04, IJ12,between the ink advantage of ink rate IJ24, IJ27, IJ29, inlet and thefiltration May result in IJ30 nozzle chamber. Ink filter may complex Thefilter has a be fabricated construction multitude of small with no holesor slots, additional restricting ink process steps flow. The filter alsoremoves particles which may block the nozzle. Small The ink inlet DesignRestricts refill IJ02, IJ37, inlet channel to the simplicity rate IJ44compared nozzle chamber May result in to nozzle has a substantially arelatively large smaller cross chip area section than that of Onlypartially the nozzle, effective resulting in easier ink egress out ofthe nozzle than out of the inlet. Inlet A secondary Increases RequiresIJ09 shutter actuator controls speed of the ink- separate refill theposition of a jet print head actuator and shutter, closing off operationdrive circuit the ink inlet when the main actuator is energized. Theinlet The method avoids Back-flow Requires IJ01, IJ03, is located theproblem of problem is careful design to IJ05, IJ06, IJ07, behind inletback-flow by eliminated minimize the IJ10, IJ11, IJ14, the ink-arranging the ink- negative IJ16, IJ22, IJ23, pushing pushing surface ofpressure behind IJ25, IJ28, IJ31, surface the actuator the paddle IJ32,IJ33, IJ34, between the inlet IJ35, IJ36, IJ39, and the nozzle. IJ40,IJ41 Part of The actuator and a Significant Small increase IJ07, IJ20,the wall of the ink reductions in in fabrication IJ26, IJ38 actuatorchamber are back-flow can be complexity moves to arranged so thatachieved shut off the motion of the Compact the inlet actuator closesoff designs possible the inlet. Nozzle In some Ink back-flow Nonerelated Silverbrook, actuator configurations of problem is to inkback-flow EP 0771 658 A2 does not ink jet, there is no eliminated onactuation and related result in expansion or patent ink back- movementof an applications flow actuator which Valve-jet may cause ink Tone-jetback-flow through the inlet. NOZZLE CLEARING METHOD Normal All of thenozzles No added May not be Most ink jet nozzle are fired complexity onsufficient to systems firing periodically, the print head displace driedIJ01, IJ02, before the ink has ink IJ03, IJ04, IJ05, a chance to dry.IJ06, IJ07, IJ09, When not in use IJ10, IJ11, IJ12, the nozzles areIJ14, IJ16, IJ20, sealed (capped) IJ22, IJ23, IJ24, against air. IJ25,IJ26, IJ27, The nozzle firing IJ28, IJ29, IJ30, is usually IJ31, IJ32,IJ33, performed during a IJ34, IJ36, IJ37, special clearing IJ38, IJ39,IJ40,, cycle, after first IJ41, IJ42, IJ43, moving the print IJ44,, IJ45head to a cleaning station. Extra In systems which Can be highlyRequires Silverbrook, power to heat the ink, but do effective if thehigher drive EP 0771 658 A2 ink heater not boil it under heater isvoltage for and related normal situations, adjacent to the clearingpatent nozzle clearing can nozzle May require applications be achievedby larger drive over-powering the transistors heater and boiling ink atthe nozzle. Rapid The actuator is Does not Effectiveness May be usedsuccession fired in rapid require extra depends with: IJ01, IJ02, ofsuccession. In drive circuits on substantially IJ03, IJ04, IJ05,actuator some the print head upon the IJ06, IJ07, IJ09, pulsesconfigurations, this Can be readily configuration of IJ10, IJ11, IJ14,may cause heat controlled and the ink jet nozzle IJ16, IJ20, IJ22,build-up at the initiated by IJ23, IJ24, IJ25, nozzle which boilsdigital logic IJ27, IJ28, IJ29, the ink, clearing IJ30, IJ31, IJ32, thenozzle. In other IJ33, IJ34, IJ36, situations, it may IJ37, IJ38, IJ39,cause sufficient IJ40, IJ41, IJ42, vibrations to IJ43, IJ44, IJ45dislodge clogged nozzles. Extra Where an actuator A simple Not suitableMay be used power to is not normally solution where where there is awith: IJ03, IJ09, ink driven to the limit applicable hard limit to IJ16,IJ20, IJ23, pushing of its motion, actuator IJ24, IJ25, IJ27, actuatornozzle clearing movement IJ29, IJ30, IJ31, may be assisted by IJ32,IJ39, IJ40, providing an IJ41, IJ42, IJ43, enhanced drive IJ44, IJ45signal to the actuator. Acoustic An ultrasonic A high nozzle High IJ08,IJ13, resonance wave is applied to clearing implementation IJ15, IJ17,IJ18, the ink chamber. capability can be cost if system IJ19, IJ21 Thiswave is of an achieved does not already appropriate May be include anamplitude and implemented at acoustic actuator frequency to cause verylow cost in sufficient force at systems which the nozzle to clearalready include blockages. This is acoustic easiest to achieve actuatorsif the ultrasonic wave is at a resonant frequency of the ink cavity.Nozzle A microfabricated Can clear Accurate Silverbrook, clearing plateis pushed severely clogged mechanical EP 0771 658 A2 plate against thenozzles alignment is and related nozzles. The plate required patent hasa post for Moving parts applications every nozzle. A are required postmoves There is risk through each of damage to the nozzle, displacingnozzles dried ink. Accurate fabrication is required Ink The pressure ofthe May be Requires May be used pressure ink is temporarily effectivewhere pressure pump with all IJ series pulse increased so that othermethods or other pressure ink jets ink streams from cannot be usedactuator all of the nozzles. Expensive This may be used Wasteful of inconjunction ink with actuator energizing. Print A flexible ‘blade’Effective for Difficult to Many ink jet head is wiped across the planarprint head use if print head systems wiper print head surface. surfacessurface is non- The blade is Low cost planar or very usually fabricatedfragile from a flexible Requires polymer, e.g. mechanical parts rubberor synthetic Blade can elastomer. wear out in high volume print systemsSeparate A separate heater Can be Fabrication Can be used ink isprovided at the effective where complexity with many IJ boiling nozzlealthough other nozzle series ink jets heater the normal drop e- clearingmethods ection mechanism cannot be used does not require it. Can be Theheaters do not implemented at require individual no additional drivecircuits, as cost in some ink many nozzles can jet be clearedconfigurations simultaneously, and no imaging is required. NOZZLE PLATECONSTRUCTION Electro- A nozzle plate is Fabrication High Hewlett formedseparately simplicity temperatures and Packard Thermal nickel fabricatedfrom pressures are Ink jet electroformed required to bond nickel, andbonded nozzle plate to the print head Minimum chip. thicknessconstraints Differential thermal expansion Laser Individual nozzle Nomasks Each hole Canon ablated or holes are ablated required must beBubblejet drilled by an intense UV Can be quite individually 1988 Sercelet polymer laser in a nozzle fast formed al., SPIE, Vol. plate, which isSome control Special 998 Excimer typically a over nozzle equipment Beampolymer such as profile is required Applications, pp. polyimide orpossible Slow where 76-83 polysulphone Equipment there are many 1993required is thousands of Watanabe et al., relatively low nozzles perprint U.S. Pat. No. 5,208,604 cost head May produce thin burrs at exitholes Silicon A separate nozzle High accuracy Two part K. Bean, micro-plate is is attainable construction IEEE machined micromachined Highcost Transactions on from single crystal Requires Electron silicon, andprecision Devices, Vol. bonded to the print alignment ED-25, No. 10,head wafer. Nozzles may 1978, pp 1185-1195 be clogged by Xerox 1990adhesive Hawkins et al., U.S. Pat. No. 4,899,181 Glass Fine glass Noexpensive Very small 1970 Zoltan capillaries capillaries are equipmentnozzle sizes are U.S. Pat. No. 3,683,212 drawn from glass requireddifficult to form tubing. This Simple to Not suited for method has beenmake single mass production used for making nozzles individual nozzles,but is difficult to use for bulk manufacturing of print heads withthousands of nozzles. Monolithic, The nozzle plate is High accuracyRequires Silverbrook, surface deposited as a (<1 μm) sacrificial layerEP 0771 658 A2 micro- layer using Monolithic under the nozzle andrelated machined standard VLSI Low cost plate to form the patent usingdeposition Existing nozzle chamber applications VLSI techniques.processes can be Surface may IJ01, IJ02, litho- Nozzles are etched usedbe fragile to the IJ04, IJ11, IJ12, graphic in the nozzle plate touchIJ17, IJ18, IJ20, processes using VLSI IJ22, IJ24, IJ27, lithography andIJ28, IJ29, IJ30, etching. IJ31, IJ32, IJ33, IJ34, IJ36, IJ37, IJ38,IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is Highaccuracy Requires long IJ03, IJ05, etched a buried etch stop (<1 μm)etch times IJ06, IJ07, IJ08, through in the wafer. Monolithic Requires aIJ09, IJ10, IJ13, substrate Nozzle chambers Low cost support wafer IJ14,IJ15, IJ16, are etched in the No differential IJ19, IJ21, IJ23, front ofthe wafer, expansion IJ25, IJ26 and the wafer is thinned from the backside. Nozzles are then etched in the etch stop layer. No nozzle Variousmethods No nozzles to Difficult to Ricoh 1995 plate have been tried tobecome clogged control drop Sekiya et al U.S. Pat. No. eliminate theposition 5,412,413 nozzles entirely, to accurately 1993 prevent nozzleCrosstalk Hadimioglu et al clogging. These problems EUP 550,192 includethermal 1993 Elrod et bubble al EUP 572,220 mechanisms and acoustic lensmechanisms Trough Each drop ejector Reduced Drop firing IJ35 has atrough manufacturing direction is through which a complexity sensitiveto paddle moves. Monolithic wicking. There is no nozzle plate. Nozzleslit The elimination of No nozzles to Difficult to 1989 Saito et insteadof nozzle holes and become clogged control drop al U.S. Pat. No.individual replacement by a position 4,799,068 nozzles slit encompassingaccurately many actuator Crosstalk positions reduces problems nozzleclogging, but increases crosstalk due to ink surface waves DROP EJECTIONDIRECTION Edge Ink flow is along Simple Nozzles Canon (‘edge the surfaceof the construction limited to edge Bubblejet 1979 shooter’) chip, andink drops No silicon High Endo et al GB are ejected from etchingrequired resolution is patent 2,007,162 the chip edge. Good heatdifficult Xerox heater- sinking via Fast color in-pit 1990 substrateprinting requires Hawkins et al Mechanically one print head U.S. Pat.No. 4,899,181 strong per color Tone-jet Ease of chip handing Surface Inkflow is along No bulk Maximum ink Hewlett- (‘roof the surface of thesilicon etching flow is severely Packard TIJ shooter’) chip, and inkdrops required restricted 1982 Vaught et are ejected from Silicon can alU.S. Pat. No. the chip surface, make an 4,490,728 normal to theeffective heat IJ02, IJ11, plane of the chip. sink IJ12, IJ20, IJ22Mechanical strength Through Ink flow is through High ink flow Requiresbulk Silverbrook, chip, the chip, and ink Suitable for silicon etchingEP 0771 658 A2 forward drops are ejected pagewidth print and related(‘up from the front heads patent shooter’) surface of the chip. Highnozzle applications packing density IJ04, IJ17, therefore low IJ18,IJ24, IJ27-IJ45 manufacturing cost Through Ink flow is through High inkflow Requires IJ01, IJ03, chip, the chip, and ink Suitable for waferthinning IJ05, IJ06, IJ07, reverse drops are ejected pagewidth printRequires IJ08, IJ09, IJ10, (‘down from the rear heads special handlingIJ13, IJ14, IJ15, shooter’) surface of the chip. High nozzle duringIJ16, IJ19, IJ21, packing density manufacture IJ23, IJ25, IJ26 thereforelow manufacturing cost Through Ink flow is through Suitable forPagewidth Epson Stylus actuator the actuator, which piezoelectric printheads Tektronix hot is not fabricated as print heads require severalmelt part of the same thousand piezoelectric ink substrate as theconnections to jets drive transistors. drive circuits Cannot bemanufactured in standard CMOS fabs Complex assembly required INK TYPEAqueous, Water based ink Environmentally Slow drying Most existing dyewhich typically friendly Corrosive ink jets contains: water, No odorBleeds on All IJ series dye, surfactant, paper ink jets humectant, andMay Silverbrook, biocide. strikethrough EP 0771 658 A2 Modern ink dyesCockles paper and related have high water- patent fastness, lightapplications fastness Aqueous, Water based ink Environmentally Slowdrying IJ02, IJ04, pigment which typically friendly Corrosive IJ21,IJ26, IJ27, contains: water, No odor Pigment may IJ30 pigment, Reducedbleed clog nozzles Silverbrook, surfactant, Reduced Pigment may EP 0771658 A2 humectant, and wicking clog actuator and related biocide. Reducedmechanisms patent Pigments have an strikethrough Cockles paperapplications advantage in Piezoelectric reduced bleed, ink-jets wickingand Thermal ink strikethrough. jets (with significant restrictions)Methyl MEK is a highly Very fast Odorous All IJ series Ethyl volatilesolvent drying Flammable ink jets Ketone used for industrial Prints on(MEK) printing on various difficult surfaces substrates such such asaluminum as metals and cans. plastics Alcohol Alcohol based inks Fastdrying Slight odor All IJ series (ethanol, can be used where Operates atFlammable ink jets 2-butanol, the printer must sub-freezing and operateat temperatures others) temperatures Reduced below the freezing papercockle point of water. An Low cost example of this is in-camera consumerphotographic printing. Phase The ink is solid at No drying Highviscosity Tektronix hot change room temperature, time-ink Printed inkmelt (hot melt) and is melted in instantly freezes typically has apiezoelectric ink the print head on the print ‘waxy’ feel jets beforejetting. Hot medium Printed pages 1989 Nowak melt inks are Almost anymay ‘block’ U.S. Pat. No. 4,820,346 usually wax based, print medium InkAll IJ series with a melting can be used temperature may ink jets pointaround 80° C.. No paper be above the After jetting cockle occurs curiepoint of the ink freezes No wicking permanent almost instantly occursmagnets upon contacting No bleed Ink heaters the print medium occursconsume power or a transfer roller. No Long warm- strikethrough up timeoccurs Oil Oil based inks are High High All IJ series extensively usedin solubility viscosity: this is ink jets offset printing. medium for asignificant They have some dyes limitation for use advantages in Doesnot in ink jets, which improved cockle paper usually require acharacteristics on Does not wick low viscosity. paper (especiallythrough paper Some short no wicking or chain and multi- cockle). Oilbranched oils soluble dies and have a pigments are sufficiently lowrequired. viscosity. Slow drying Micro- A microemulsion Stops inkViscosity All IJ series emulsion is a stable, self bleed higher than inkjets forming emulsion High dye water of oil, water, and solubility Costis surfactant. The Water, oil, slightly higher characteristic drop andamphiphilic than water based size is less than soluble dies can ink 100nm, and is be used High determined by the Can stabilize surfactantpreferred curvature pigment concentration of the surfactant. suspensionsrequired (around 5%)

1. A micro-electromechanical fluid ejection mechanism comprising: asubstrate defining an ink passage in fluid communication with a taperedink chamber having an ink ejection port; and a shape memory alloy (SMA)actuator arranged within the chamber, the actuator configured tostraighten when heated and to return to a bent state upon subsequentcooling to facilitate ejection of ink via the ejection port.
 2. Themicro-electromechanical fluid ejection mechanism of claim 1, wherein thesubstrate comprises a multilayered substrate including control and drivecircuitry to facilitate actuation of the SMA actuator.
 3. Themicro-electromechanical fluid ejection mechanism of claim 2, wherein theactuator includes a serpentine heating element which is electricallycoupled to the control and drive circuitry.
 4. Themicro-electromechanical fluid ejection mechanism of claim 4, wherein theactuator further comprises a pair of silicon-based layers with theheating element interposed between the silicon-based layers.
 5. Themicro-electromechanical fluid ejection mechanism of claim 4, wherein oneof the silicon-based layers comprises silicon dioxide material whereasthe other silicon-based layer comprises silicon nitride
 6. Themicro-electromechanical fluid ejection mechanism of claim 5, whereineach silicon-based layer extends from a layer of corresponding materialin the multi-layered substrate.
 7. The micro-electromechanical fluidejection mechanism of claim 2, further comprising a pair of metalinterconnects which each couple a respective end of the heating elementto the control and drive circuitry.